From looking at the wikipedia discussion page, it looks like
the contributers are responsible for hand-formatting the page
to make it look all pretty? And the use of ^:+ or ^*+ is
so that they can use wiki-style lists to do the indentation?

If that's the case, it's just a matter of wikipedia using a
different syntax to do the same sort of manual formatting of
the discussion, and you would train the users to do markdown-
style syntax instead. (Or write a q&d preprocessor that
expands ^:+ and ^*+ out into the appropriate levels of list
for you.)